[eas-cli] Use the selected EAS environment in eas update

[ramonclaudio]

Stacked on #4229.

Why

eas update doesn't always use the EAS env chosen from the interactive prompt for app config, export, and Fingerprint.

How

I updated the command to load the EAS env chosen from either --environment or the prompt, use production mode for app config and export, and pass the selected env vars to config updates, runtime version resolution, and Fingerprint.

Test Plan

Tests and package checks pass.

[linear-code]

DVT-119

[github-actions]

✅ Thank you for adding the changelog entry!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.05%. Comparing base (b0bb4d2) to head (1103746).

Additional details and impacted files

@@                            Coverage Diff                             @@
##           @ramonclaudio/dvt-119-eas-cli-env-mode    #4269      +/-   ##
==========================================================================
+ Coverage                                   63.90%   64.05%   +0.15%     
==========================================================================
  Files                                        1033     1033              
  Lines                                       47555    47574      +19     
  Branches                                    10002    10007       +5     
==========================================================================
+ Hits                                        30384    30467      +83     
+ Misses                                      17070    17005      -65     
- Partials                                      101      102       +1     

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